The invention relates to a test device for bodily fluids comprising a solid carrier with a bonded reagent, a light source for transmitting light to the carrier and a light detector for detecting light received from the carrier.
Such test devices are well known in the art. U.S. Pat. No. 5,131,756 discloses a test carrier analysis device for determining the reflectivity of a test field surface. An optical unit of the device contains several light transmitters and a measurement receiver, whereby the light transmitters are directed obliquely from above onto the measurement surface. The light transmitters are arranged opposite to one another with off-set planes of incidence.
Other test devices known in the art employ light sources wherein the light impinges on the measurement surface uniformly from all directions in space. Commonly, the light sources that are used are light-emitting diodes, which are favoured in view of their low-energy use, low costs and high reliability.
Test devices to which the invention relates are particularly useful for pregnancy tests but are not confined hereto. A prime consideration with these test devices is that they must be small, manageable and cheap to manufacture in view of the required suitability for self-diagnosis by a user.
The problem with known devices is the lack of accuracy, particularly in the area where the signals measured by the detector do not warrant an unambiguous positive or negative test result.